Similar to a spirometer, Spiro works by measuring the inspiratory (inhaling) and expiratory (exhaling) forces created by your lungs. An air pressure sensor inside the unit reads the pressure offsets created by your breathing and are transmitted to the iPhone/iPad for gameplay. The data is used to incentivize a fun exercise experience for athletes, children, and others looking to improve their lung strength.

The device itself offers 10 levels of air resistance via 10 different sizes of air holes in the base dial of the device. These varying levels of resistance correspond to game levels in the iPad/iPhone app. The device contains no batteries and is powered completely from the iPhone or iPad. The power consumption is very low.